1. Field of the Invention
The present invention relates generally to write head drivers for physical data storage devices such as tape drives, hard disk drives, and the like, and particularly, to a novel current mode write head driver provided with current measurement capability while performing a write operation.
2. Description of the Prior Art
In write head drivers there is a requirement to measure and monitor the write current during the write operation. For the case of voltage mode write head drivers this is done by measuring the voltage applied to the write circuit. This is easily accomplished because the write current is determined by the external resistance in series with the write head. For the case of current mode write drivers another method must be used to measure the current.
FIG. 1 illustrates a simple voltage mode write driver circuit 20 according to the prior art. For this write driver, the current Ih through the write head is determined by the value of the resistors R1, R2, and the voltage source V1 22 assuming that the NFET devices M1, M2, and PFET devices M3, M4 have a low voltage drop from source to drain when they are turned on. Neglecting the voltage drop in the FET devices and the write head, the current through the head, Ih, is just Ih=V1/(R1+R2).
FIG. 2 illustrates a simple current mode write driver circuit 50 according to the prior art. For this driver, the current through the write head L1 is determined by the value of the current source I1 52. It is understood that no resistors are in series with the write head, L1. For this current mode driver the current through the write head, L1, is not a function of the voltage V1 22.
It would be highly desirable to provide a system and method that enables the measurement of the current through the write head during the write operation.